Residue accumulates on tubular walls in borehole from drilling mud or well fluids. This residue needs to be removed before setting tools against an existing tubular in the borehole. More often than not a separate trip is made to clean the well before running in and setting the tool in question. Using two trips takes a lot of time and costs money so a one trip approach is a logical goal of streamlining the process.
One approach to the solution has been to simply circulate the well with the tool in the hole with the hope that circulation will do a good enough job in the zone where the tool is to be set. This technique is shown in U.S. Pat. No. 8,347,968 and suffers from an inability to focus on a small portion of a wellbore where the tool is to be set and the spotty effectiveness of circulation as a technique for effectively removing debris from a specific portion of the well where such removal is most critical.
One method has combined milling and scraping but while mentioning a packer in passing to be set in a polished bore, it does not indicate that the packer is delivered in the same trip as the milling and scraping tools. That reference is U.S. Pat. No. 7,096,950.
U.S. Pat. No. 6,896,064 illustrates a cleanup tool mounted below a packer with the purpose of cleaning the wellbore and then setting the packer in a single trip. There are several issues with this design that discloses a fixed dimension scraper immediately below the packer. One is that the loosened debris will need to be passed around the packer sealing element or through bypasses built into the mandrel body of the packer. Either way there is a serious chance that the packer will become stuck as debris tries to get around or through it even before it is set. Debris can stick to the outside of the packer element preventing it from getting a good seal. Once the cleaning is done and the packer is set, the cleaning tools are still hanging on the underside of the packer and may later also require milling out whether still supported by the packer or even if dropped to the hole bottom in the event there is a further extension of the borehole.
The cleaning tools theoretically could also be retrieved in the event that the tool is a retrievable packer/bridge plug. However, retrieval could be extremely difficult if the tool is exposed to wellbore fluids for an extended amount of time, which could limit the ability of scrapers to expand and contract to different wellbore geometries.
The shortcomings described above are avoided with the present invention where the cleaning tools are located above the packer or plug or other tool to be set, with a disconnect in between so that the running string and the cleaning equipment can be released and removed from the borehole. By incorporating a circulation sub also above the packer and below the cleaning equipment, the loosened debris can be circulated out uphole of the packer to spare the packer or plug the issue of potential sticking with debris that has to pass by or through it as in U.S. Pat. No. 6,896,064. Those skilled in the art will have a better understanding of the invention from a review of the description of the preferred embodiment and the associated drawing while appreciating that the full scope of the invention is to be determined from the appended claims.